This invention relates to a slanted internal combustion engine of the type wherein several in-line cylinders are inclined with respect to the vertical, and an overhead camshaft actuates an intake valve and an exhaust valve for each cylinder. Intake and exhaust passages are situated on the same side of the cylinder head.
In existing slant engines, the axes of the intake and exhaust valves of each cylinder are parallel, both valve axes lying perpendicular to the axis of the camshaft in order to ensure a correct direct drive of the valves. The belief has been that both valve axes should be located in the same plane passing through the camshaft axis, in order to facilitate the machining of the valve-receiving cylinder head.
On a slanted engine, the accepted arrangement of coplanar intake and exhaust valve axes presents a number of problems having to do in particular with the dimensioning of the valve-actuating elements, the accessibility of the engine components when repairs or adjustments are to be carried out, the steps of feeding and combustion, and the engine's performance in general.
The object of the present invention is to provide a configuration which will eliminate these disadvantages and make it possible to give the engine, in its entirety, a strong slant or inclination with respect to the vertical in order to obtain a propulsive group with minimal height.
In the engine of the invention, the axes of the intake valve and the exhaust valve of each cylinder lie in planes parallel to each other and perpendicular to the axis of the camshaft, and these valve axes diverge from each other as they approach their respective cylinder. Accordingly, the intake valve axis and the exhaust valve axis have different inclinations. This provides greater freedom in selecting the diameters of the valve heads in accordance with criteria which provide good feeding and good combustion, without necessitating other measures such as longitudinal redimensioning of the camshaft.
The axis of the camshaft is located above the inclined plane which includes the cylinder axes, making it possible to give the intake passages in the cylinder head a non-countersloped shape, in spite of the obstacle created by the seating of the springs of the valves, even when the engine is sharply inclined.
In an advantageous embodiment of the invention, the axis of the intake valve is inclined with respect to the common plane occupied by the plural cylinder axes, the intake valve axis crossing the cylinder axis plane midway between the axis of the camshaft and the valve head. In the same way, it is advantageous for the axis of the exhaust valve to be inclined with respect to the common plane of the cylinder axes in such a way that the exhaust valve axis crosses the cylinder axis plane approximately on a level with the head of the exhaust valve. Such an arrangement makes it possible to make the intake and exhaust passages flow into the combustion chamber and to position the spark plug in that chamber for optimum feeding and combustion.
Other characteristics and advantages of the invention will be apparent from reading the following explanatory and nonlimiting description of an embodiment of the engine of the invention.